Audiobus: Use your music apps together.

What is Audiobus? — Audiobus is
an award-winning music app for iPhone and iPad which lets you use
your other music apps together. Chain effects on your favourite
synth, run the output of apps or Audio Units into an app like
GarageBand or Loopy, or select a different audio interface output
for each app. Route MIDI between apps — drive a
synth from a MIDI sequencer, or add an arpeggiator to your MIDI
keyboard — or sync with your external MIDI gear.
And control your entire setup from a MIDI controller.

Audio Analysis Tips, Tricks and Thoughts

@Blue_Mangoo got some interesting discussions started about audio analysis techniques with a couple of recent video postings (notably with his compressor shoutout video).

A few of us have been carrying on discussion in those threads. I've started this topic so that we can talk about audio analysis and tools without distracting from the main topics of those other threads.

Most recently, @tja and I have been talking about spectrum analysis tools on iOS and also Audulus patches for generating test signals.

Comments

@tja: so, I made a few discoveries today about both Audulus and SpectrumView.

After quite a bit of testing I discovered that SpectrumView has trouble if you give it a stereo file. I created a couple of sine sweeps with an improved version of my Audulus patch and noticed that when I generated a mono sweep that went to 0 dB, the sweep was clean. A stereo version of the same file showed all those extra harmonics and aliasing. (Note that the mono sweep still sounds wrong when SpectrumView plays it back but the analysis looks clean). I think that SpectrumView may be summing the left and right channels and then performing the analysis.

SpectrumView's playback anomalies are something different. When it plays back the sine sweep (even the "clean" one), it has strange artifacts that you won't hear if you play it back in any other app.

On the Audulus front, I noticed that the low frequencies in my sweep did not have the same amplitude as higher frequencies. Someone on the Audulus forum remarked that using the DAC node for output ensures that Audulus puts out exactly what is calculated. The speaker module that I used actually has a filter on it.

I have created an improved version of the sweep app, and I have made it more convenient for you to customize. I have embedded some nodes inside that you can type into to change the knob range, and I have improved the scaling of the frequency knobs to be more usable.

@espiegel123 said:@tja: so, I made a few discoveries today about both Audulus and SpectrumView.

After quite a bit of testing I discovered that SpectrumView has trouble if you give it a stereo file. I created a couple of sine sweeps with an improved version of my Audulus patch and noticed that when I generated a mono sweep that went to 0 dB, the sweep was clean. A stereo version of the same file showed all those extra harmonics and aliasing. (Note that the mono sweep still sounds wrong when SpectrumView plays it back but the analysis looks clean). I think that SpectrumView may be summing the left and right channels and then performing the analysis.

SpectrumView's playback anomalies are something different. When it plays back the sine sweep (even the "clean" one), it has strange artifacts that you won't hear if you play it back in any other app.

On the Audulus front, I noticed that the low frequencies in my sweep did not have the same amplitude as higher frequencies. Someone on the Audulus forum remarked that using the DAC node for output ensures that Audulus puts out exactly what is calculated. The speaker module that I used actually has a filter on it.

I have created an improved version of the sweep app, and I have made it more convenient for you to customize. I have embedded some nodes inside that you can type into to change the knob range, and I have improved the scaling of the frequency knobs to be more usable.

Here is the improved sweep patch:

Thanks a lot

I have like no time and now I will end up reinstalling Audulus and heading down that rabbit hole....

@espiegel123 said:@tja: so, I made a few discoveries today about both Audulus and SpectrumView.

After quite a bit of testing I discovered that SpectrumView has trouble if you give it a stereo file. I created a couple of sine sweeps with an improved version of my Audulus patch and noticed that when I generated a mono sweep that went to 0 dB, the sweep was clean. A stereo version of the same file showed all those extra harmonics and aliasing. (Note that the mono sweep still sounds wrong when SpectrumView plays it back but the analysis looks clean). I think that SpectrumView may be summing the left and right channels and then performing the analysis.

SpectrumView's playback anomalies are something different. When it plays back the sine sweep (even the "clean" one), it has strange artifacts that you won't hear if you play it back in any other app.

On the Audulus front, I noticed that the low frequencies in my sweep did not have the same amplitude as higher frequencies. Someone on the Audulus forum remarked that using the DAC node for output ensures that Audulus puts out exactly what is calculated. The speaker module that I used actually has a filter on it.

I have created an improved version of the sweep app, and I have made it more convenient for you to customize. I have embedded some nodes inside that you can type into to change the knob range, and I have improved the scaling of the frequency knobs to be more usable.

Here is the improved sweep patch:

Thanks a lot

I have like no time and now I will end up reinstalling Audulus and heading down that rabbit hole....

Audulus is a great rabbit hole. When I find some time, I am going to put together a few videos showing fun things one can do with Audulus without knowing how to program it. It is such a fun audio fx toolkit.